Pathways of carbohydrate metabolism operative in oral bacteria and mechanisms by which cellular metabolism is regulated continue to be under investigation. Current emphasis is placed on delineating the mechanism underlying the inactivation of a cell-associated fructosyltransferase (FT) produced by Streptococcus salivarius. Our present data point to the fact that FT inactivation is a two step phenomenon. The first step appears to be an oxidation-reduction reaction that requires a reduced pyridine nucleotide (NAD(P)H), Cu++, and a phospholipid or detergent. Such requirements are also exhibited by certain microbial and mammalian liver mixed function oxidases. This step results in a loss of FT catalytic activity. We propose that this reaction modifies the enzyme and "marks" it as a substrate for a protease which, in a second step, then degrades the protein.